Helpful? 0

Knob-and-tube wiring in insulation

Now I am back to the issue of dense-packed cellulose in a house where knob and tube is in most of the exterior walls. I see lots of older homes installing cellulose and or fiberglass blown into the walls....just as an energy upgrade not as a whole house redo (gutted and re-wired etc.)

What are the electrical codes saying with regard to knob and tube exposure to insulation that is blown in... is this safe?

susan

Asked by susan clellen
Posted Wed, 06/08/2011 - 09:31
Edited Wed, 06/08/2011 - 21:26

Tags:

6 Answers

Select your preferred way to display the comments and click "Save settings" to activate your changes.
1.
Helpful? 0

NEC 2011 Article 394 Concealed Knob-and-Tube Wiring
394.12 Uses Not Permitted
(5) Hollow spaces of walls, ceilings, and attics where such spaces are insulated by loose, rolled, or foamed-in-place insulating material that envelops the conductors.

The problem is that the average insulation installer does not know or does not care about electrical codes. Combine insulation with wiring protected with breakers larger than originally intended is a disaster waiting to happen.

Answered by Nathan Spriegel
Posted Wed, 06/08/2011 - 09:50
Edited Wed, 06/08/2011 - 11:07.

2.
Helpful? 0

Thanks Nathan. I am so done with industrial methods and materials...Each generation comes out with the next best thing since burnt toast ! Plan C is to apply 2 " of light straw/cob and earth-plaster over the old plaster walls and be done.

susan

Answered by susan clellen
Posted Wed, 06/08/2011 - 13:32

3.
Helpful? 0

I would take this as a chance to perform an electrical evaluation and determine if electrical upgrades should be performed anyway. Most houses with knob and tube do not have enough circuits to serve modern requirements My own house only had three circuits to serve all general-use receptacles, including the two bedrooms. That is why people often replace the 15 amp fuse/breaker with 20 amp ones. Added benefits would include proper grounding-type receptacles and AFCI protection.

Answered by Nathan Spriegel
Posted Wed, 06/08/2011 - 15:04
Edited Wed, 06/08/2011 - 15:29.

4.
Helpful? 0

You should probably read this before going any further with your renovation:
http://tinyurl.com/6xvffhq

Answered by James Morgan
Posted Wed, 06/08/2011 - 16:02

5.
Helpful? 0

Knob and tube should really be replaced whenever feasible.

Answered by Eric Dymond
Posted Wed, 06/08/2011 - 17:10

6.
Helpful? 0

Susan,
I've spoken to a lot of weatherization workers and cellulose installers over the years, and fortunately they all know the rule -- you can't install cellulose over knob-and-tube wiring. Insulation upgrades are a good opportunity to perform wiring upgrades.

Answered by Martin Holladay, GBA Advisor
Posted Wed, 06/08/2011 - 21:28

Other Questions in General questions

How do you insulate cob or earth bag walls in the Northeast?

In Green building techniques | Asked by Aaron B | Sep 27, 14

Grid-tied without independence … what’s the point?

In General questions | Asked by flitch plate | Sep 29, 14

Windows for my Pretty Good House

In Green products and materials | Asked by Matt Mesa | Sep 29, 14

Please tell me why I have to put so much insulation / outsulation at the roof/celing?

In Energy efficiency and durability | Asked by leo kloop | Sep 30, 14

Is continuous polyiso over plywood and concrete wall OK?

In Plans Review | Asked by Jamie Malcolm-Brown | Sep 30, 14
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!